Method for deriving rotor angular orientation

ABSTRACT

The present invention relates to a method for determining the load angle of a three-phase current synchronous machine ( 10 ) with the aid of position information ( 2 ) of an internal combustion engine. The latter is furnished with an engine control device ( 7 ), in which operating parameters and the position information of components of the internal combustion engine are stored. The following method steps are run through:  
     First of all, rotational position ( 2 ) of the internal combustion engine is recorded in the engine control device when the internal combustion engine is switched off. Before the start of the internal combustion engine, the transmission of the rotational position information ( 2 ) of the internal combustion engine to the electrical three-phase current machine ( 10 ) takes place for the adjustment between the rotational position information ( 2 ) and load angle ( 5 ) of electrical three-phase current machine ( 10 ), at a rotational speed of the internal combustion engine of n=0.

FIELD OF THE INVENTION

[0001] Machine regulation of a high-output generator having the startingfunction of a three-phase current synchronous machine requiresinformation on the load angle. If incremental encoders are used,recording the load angle is possible only in moved/rotating systems.However, to make available maximum torque, for example at the startingof the internal combustion engine, information on the pole wheelposition is already required at a rotational speed n=0.

BACKGROUND INFORMATION

[0002] A system for reducing torsional vibrations in the power train maybe seen in the journal “System Partner 98”, pages 64 to 66. The systemcombines two electrical machines in itself, which are used on the onehand for the “start” function, and on the other hand for voltage supplyin the vehicle electrical system of motor vehicles. Using the proposeddesign approach, the power of the electrical machine may be used toapply torque impulses to the crankshaft of the internal combustionengine, so that noticeable rotational irregularities may be minimized.

[0003] The electrical machine used generates a great acceleration of thecrank mechanism, the internal combustion engine being accelerated toidling speed; only after that, does ignition take place. The generatorfunction of the system offers high electrical power even at very lowrotational speeds; the three-phase machine is driven from apulse-controlled inverter, and therefore, with respect to its rotationalspeed and its torque, it is able to be freely controlled and regulated.

[0004] A method for estimating the pole wheel position in a claw polemachine may be seen in DE 100 36 869 A1. This invention relates to amethod for determining the position of a rotating component of a clawpole machine which is operated in the RST system, and for whoseregulation the transformation of the stator variables from the RSTsystem into the d, q system and vice versa is required. The claw polemachine as an overall system is subdivided into a non-observablesubsystem and an observable subsystem containing a filter element. Thefilter element contained in the observable subsystem delivers the outputvariables.

[0005] The proposed method permits the determination of the pole wheelposition only when the internal combustion engine is rotating, so thatthe search cycle prolongs the starting process inadmissibly when ahigh-output generator is used, and again partially reduces to nothingthe driving advantage achievable by the use of these high-outputmachines.

SUMMARY OF THE INVENTION

[0006] Using the method proposed by the present invention, in the idealcase the search cycle may be completely eliminated by evaluating datathat are already available in the engine control unit. On account of theutmost stable, known coupling of the crank mechanism and the electricalmachines by a belt drive, the pole wheel position and the rotationalposition of the crankshaft of the internal combustion engine are in afixed, known ratio to each other.

[0007] When the internal combustion engine is turned off, the rotationalposition of the internal combustion engine can be recorded in the enginecontrol unit and stored permanently.

[0008] The storage of the last instantaneous rotational positioninformation may be written into a memory which retains this informationeven if current supply of the engine control unit is interrupted. Duringthe next starting procedure of the internal combustion engine there isthus available an exact value for the crankshaft's angular position ofthe internal combustion engine, so that the starting phase of aninternal combustion engine may be drastically shortened by the omissionof the search cycle.

[0009] Compared to design approaches used up to the present in therelated art, by reverting to rotational position information gathered atthe time of the previous shutting down of the internal combustionengine, the search cycle preceding the starting procedure is either madecompletely superfluous, so that the internal combustion engine may bestarted directly at the required torque, or the initial value forbeginning the search cycle may be selected so that the search cycle isdrastically shortened from a time point of view, and can be held smallwith respect to the angle swept over.

[0010] Thereby, an absolute angle encoder may be saved in the electricalpolyphase machine, such as a high-output generator, which is to besynchronized with respect to the pole wheel position. Internalcombustion engine and electrical three-phase machine are in a fixedlypredefined coupling connection to each other, e.g. via a belt drive,which is held at the appropriate initial tension to exclude slippage. Ifthe internal combustion engine is switched off, then, via thetransmission ratio of the belt drive, the belt length, the diameter ofthe belt pulley of the electrical poly-phase machine as well as of thediameter of the belt pulley mounted laterally on the crankshaft, thepole wheel position is coupled to the position of the belt pulley on thecrankshaft side. From this, the pole wheel position is able to beadjusted to the rotational position of the internal combustion engine inone balancing operation; since this operation takes place at arotational speed n=0, the influences of the coupling—in the case of thebelt drive selected here the appearance of slippage—is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention is explained below in detail on the basisof the drawings. The figures show:

[0012]FIG. 1 the rotational position pattern of the crankshaft of aninternal combustion engine, plotted against time,

[0013]FIG. 2 the rotational position pattern of the pole wheel of ahigh-output generator, plotted against time,

[0014]FIG. 3 the adjustment between the engine control unit of theinternal combustion engine and the electrical machine and

[0015]FIG. 4 the derivation of the load angle from the rotationalposition information of the internal combustion engine for theactivation of a search cycle, if required.

EMBODIMENT VARIANTS

[0016]FIG. 1 shows the rotational position pattern of the crankshaft ofan internal combustion engine, plotted along the time axis.

[0017] In the drawing in FIG. 1, the characteristic pattern ofcrankshaft angle 2 for one crankshaft rotation is reproduced. Thesawtooth-shaped pattern that comes about for a crankshaft angle 1(T_(KW)) represents a complete crankshaft angle rotation from 0° to360°. This pattern sets in periodically, the times required for acomplete rotation of the crankshaft decreasing continuously with growingrotational speed of the internal combustion engine.

[0018] In the representation in FIG. 2 there may be seen the rotationalposition pattern of the pole wheel of an electrical three-phase currentmachine, such as a high-output generator, likewise plotted along timeaxis 3.

[0019] In dependence on the coupling of electrical three-phase currentmachine 10 with the internal combustion engine, an extremely firmconnection occurs between a complete revolution of the pole wheel of theelectrical three-phase current machine and the crankshaft. In theexample shown in FIG. 2, the pole wheel of the electrical three-phasemachine rotates six times for one complete revolution of the internalcombustion engine's crankshaft. The respective complete revolution ofthe pole wheel of the three-phase machine is shown having referencenumeral 16. A comparison of the angle position pattern according to FIG.1 and FIG. 2 shows that sawtooth profile 6 is offset by a temporal shiftwhich corresponds to angle adjustment region 4.

[0020] In an engine control device associated with the internalcombustion engine, the relationship between rotational angle 2 of theinternal combustion engine and rotational angle 5 of the electricalthree-phase machine may be stored as a characteristic line fieldrelationship as a function of the belt length, a function of thediameters of the belt pulleys and, in the normal case, the tensionprevailing in the belt drive.

[0021]FIG. 3 shows the adjustment between the engine control device ofthe internal combustion engine and the electrical machine, with respectto the rotational position information.

[0022] An engine control device 7, which is associated with the internalcombustion engine, records its operating parameters. In addition tothat, at engine control device 7 shown schematically here, memorylocations are provided in which characteristic line relationships, suchas the above-mentioned characteristic line relationship for the beltdrive of the electrical three-phase machine are stored. When theinternal combustion engine is switched off, the position of the crankmechanism, i.e. the crankshaft, is ascertained by engine control device7 and permanently stored in it. The storing preferably takes place inthat, even when the current supply to engine control device 7 isinterrupted, that is, when the internal combustion engine is switchedoff, the last instantaneous position of the cranking mechanism isstored. This rotational position information 2 is made available forinformation when the internal combustion engine is started again byelectrical three-phase machine 10, e.g. a high-output generator. Forthis purpose, a position sensor 8 inside engine control device 7transmits rotational position 2 to a synchronization step 9 ofelectrical three-phase machine 10, in which an adjustment is able to bemade of rotational information 2 of the internal combustion machine, ofthe angle position of the crank mechanism and, as a further input value,of load angle 11. Because of the coupling of the internal combustionengine and the electrical three-phase current machine via, for instance,a belt drive, pole wheel position 5 as well as rotational position 2 ofthe internal combustion engine are predefined in a defined relationshipto each other, so that, within the framework of the synchronizationstep, an adjustment is able to be made of pole wheel position 5 ψ_(HGS)as a function of rotational position information 2 (ψ_(VM)) and theadjustment angle (ψ_(adjustment)). Given sufficient accuracy ofrotational position information 2 of the crank mechanism transmitted byengine control unit 7 of the internal combustion engine coupled withelectrical three-phase current machine 10, search cycle 14 (cfrepresentation as in FIG. 4) may be omitted.

[0023] The adjustment taking place in synchronization step 9 betweenrotational position information 2(ψ_(VM)) and load angle 5(ψ_(HGS))takes place at a rotational speed of the internal combustion engine=0,so that the influences of the coupling of the internal combustion engineand associated electrical three-phase current machine 10 may, to thegreatest extent, be ignored. Such an influence making the adjustmentdifficult would be, for example, an occurring slippage between the beltpulley at the crankshaft of the internal combustion engine and the beltpulley driving electrical three-phase current machine 10. However, sincethe adjustment procedure is omitted at rotational speed n=0, whenslippage occurs in the belt drive, the relationship between rotationalposition information 2 of the internal combustion engine and the polewheel position of the three-phase current machine is not invalidated.

[0024] From the representation as in FIG. 4, the derivation of the loadangle from the rotational position information of the internalcombustion engine to the possibly required execution of a search cyclemay be seen.

[0025] Analogously to the representation in FIG. 3, engine control unit7 transmits, via position sensor 8 integrated into it, rotationalposition information 2, i.e. the crankshaft angle of the internalcombustion engine, to electrical three-phase current machine 10, forinstance, a high-output generator. Rotational position information 2(ψ_(VM)) is used as the input variable for a synchronization step 9,which is provided in three-phase current machine 10. In synchronizationstep 9, an initial value 13 is ascertained for a search cycle 14. As afunction of the transmitted values of rotational position information 2of the internal combustion engine by position sensor 8 of engine controlunit 7, initial value 13 for search cycle 14 to be carried out can beselected in such a way that search cycle 14 may be kept short or small,respectively with respect to time and the angular region swept over.Using the input information of rotational position 2 of the crankmechanism of the internal combustion engine, search cycle 14 is able tobe clearly shortened, or to be completely omitted in the ideal case (cfthe representation as in FIG. 3).

[0026] If rotational position information 2 of the internal combustionengine is ascertained using absolute angle sensors in the internalcombustion engine, the adjustment in synchronization step 9 may beoptimized in an advantageous manner. In addition, absolute angleencoders, which would otherwise have to be provided in electricalthree-phase current machine 10, may be saved.

[0027] As a result, with the aid of initial value 13, predefined bysynchronization step 9 and in dependence on its rotational positioninformation 2 of the internal combustion engine, a load angleinformation 15 is generated, which the electrical three-phase currentmachine 10 should assume to generate the greatest torque required forstarting and to shorten the starting procedure.

[0028] Using the method proposed according to the present invention,which is carried out when the rotational speed of the internalcombustion engine n=0, the duration of search cycle 14 may beconsiderably restricted, since it is limited to a window which islimited by position sensor 8 via engine control unit 7. An inadmissibleprolonging of the starting procedure of an internal combustion engine byan electrical three-phase current machine 10, such as a high-outputgenerator, may now be omitted in the ideal case by using the methodproposed according to the present invention (cf representation as inFIG. 3).

[0029] On the other hand, if a search cycle 14 is required, this can belimited temporally and with respect to the search window in such a waythat the occurrence of unwanted events, during the revolution of thecrank mechanism of the internal combustion engine during search cycle14, may to the greatest extent be excluded.

REFERENCE NUMERAL LIST

[0030]1 t_(kw)=crankshaft revolution

[0031]2 rotational position information, internal combustion engine

[0032]3 time axis

[0033]4 angle adjustment region

[0034]5 load angle

[0035]6 sawtooth profile

[0036]7 engine control unit

[0037]8 position sensor

[0038]9 synchronization step

[0039]10 electrical three-phase current machine

[0040]11 input value load angle

[0041]12 adjustment

[0042]13 initial Value

[0043]14 search cycle

[0044]15 load angle output value

[0045]16 revolution, electrical machine

What is claimed is:
 1. A method for determining the load angle of athree-phase current synchronous machine (10) with the aid of positioninformation (2) of an internal combustion engine, which is furnishedwith an engine control device (7) in which operating parameters and theposition information of components of the internal combustion engine arestored, having the following method steps: the recording of therotational position of the internal combustion engine in the enginecontrol device (7) when the engine is switched off, the transmission ofthe rotational position information (2) of the internal combustionengine to the electrical three-phase current machine (10) for adjustmentbetween rotational position information (2) and the position angle (5)of the electrical three-phase current machine (10) at a rotational speedof the internal combustion engine of n=0.
 2. The method as recited inclaim 1, wherein the electrical three-phase current machine (10) and theinternal combustion engine are coupled with each other.
 3. The method asrecited in claim 1, wherein a rotational position determination of theelectrical three-phase current machine is made before the startingprocedure within the framework of a search cycle (14).
 4. The method asrecited in claim 3, wherein the search cycle (14) is considerablyminimized by the transmission of rotational position information (2) ofthe internal combustion engine by the engine control unit (7) to theelectrical three-phase current machine (10).
 5. The method as recited inclaim 3, wherein by the stipulation of the rotational positioninformation (2), the initial value (13) for the search cycle (14) isselected in such a way that the search cycle (14) is held short withrespect to time and, more so, small by the angular region swept over. 6.The method as recited in claim 1, wherein the start of the internalcombustion engine takes place directly because of the stipulation ofrotational position information (2) of the internal combustion engine bythe engine control unit (7).
 7. The method as recited in claim 1,wherein when the internal combustion engine is switched off, therotational position information (2) of the internal combustion engine isascertained by the use of absolute angle sensors.
 8. The method asrecited in claim 1, wherein when the internal combustion engine isswitched off, the information (2) corresponding to the rotationalposition of the internal combustion engine is able to be maintained andis able to be accessed when the internal combustion engine is started.